Dual carburetor



March 1943. G. M. BICKNELL ETAL 3 I DUAL CARBURETOR Filed Nov. 1a, 1940I a My 94/ I l5 i. Q

INVENTORS GEORGE M.BICKNELL VAN C.WORDEN ATTORNEY Patented Mar. 30, 1943DUAL CARBURETOR George M. Bicknell, St. Louis, Mo., and Van C.

Worden, Detroit, Miclm assignors to Carter Carburetor Corporation, St.

poration of Delaware Application November 19, 1940, Serial No.366,262

1 Claim. (Cl. 261-41) I This invention relates to carburetors for.internal combustion engines and consists particularly in novelthrottling devices for controlling the fuel and fuel mixture passages ofa multiple barrel carburetor.

In the usual form of automotive carburetors now in use, liquid fuel isdischarged into a venturi located anterior to the throttle valve wherethe suction available for drawing fuel from the nozzle is substantiallydirectly proportional to the degree of opening of the throttle valve andthe engine speed. It is desirable that the main fuel nozzle dischargeinto a restricted zone, preferably of Venturi shape, so that under theleast favorable suction conditions, that is, when the throttle issubstantially closed or when the throttle is more fully opened but theengine is operating slowly, quantities of fuel are discharged from themain nozzle. Accordingly, the size of the mixture conduit is necessarilya compromise between the relatively small size which is an ad,- vantageat low speeds, and the larger size which has maximum capacity for highspeed operation.

In order to overcome the disadvantages of this compromise, which resultsin decreased fuel discharge at, low speeds and also decreased capacityat high speeds, separate carburetors may be provided, in one of which,the mixture controlling valve or throttle may be manually operated, inthe usual manner, and in the other of which the mixture controllingvalve is at least partly controlled according to suction conditions inthe first carburetor anterior to the throttle or throttle position, sothat the second carburetor functions, substantially, only at the higherspeeds and serves, in effect, to increase the capacity of thecarbureting. system, without reducing the effective fuel discharge atthe lower speeds.' For convenience, it is desirable to form the twocarburetors, into a single body structure in which the multiple mixtureconduit has a common air inlet upon which the air cleaner and silencerdevice is mounted. The linkage connections for controlling the throttlevalves, one manually and the other according to suction conditions, aregreatly simplified over the case where wholly separate carburetors areused, but since suction may be transmitted from one mixture conduit orbarrel to the other through the common air inlet, it is necessary thatthe main fuel nozzle of the suction controlled conduit or barrel be cutoff at all times when this barrel is supposedly out of operation. It isdesirable, however, to provide an idlingsystem in each barrel or mixtureconduit, and for this reason, the idling system in (not shown).

Louis, Mo., a corthe suction controlled barrel, must obtainits fuelindependently of the main nozzle discharging into this barrel.

An object of the present invention is, therefore,

to provide a carburetor having multiple fuelmix-- ture conduits with acommon air inlet, in which means is provided to prevent discharge fromthe fuel nozzle supplying one of the conduits, except under conditionswhen this nozzle is caused to discharge by the suction condition in thebarrel with which it is associated;

Another objectis to provide a novel, multiple barrel carburetor in whicheach barrel is vprovided with its own idling system adapted to functionwhenever the throttle therein is substantially closed, while, at thesame time, providing for cutting ofi of the main nozzle in the secondaryor suction operated barrel.

These objects and other more detailed objects hereafter appearing areattained substantially by the structure illustrated in the accompanyingdrawing in which the figure is a cross sectional diagrammatic view of acarburetor embodying the invention.

The carburetor shown is of the downdraft type having a divided mixtureconduit, the lower portion thereof forming a pair of mixing conduits land 2 including venturis 3 and l and havin a common air inlet horn 5.Butterfly throttle valves 6 and l are mounted, respectively, in thelower or discharge portions of the mixture conduits and a choke valve 8is similarly mounted in air horn 5. The choke valve may be operated byany suitable manual or automaticcontrol device The air horn is providedwith an annular rib 9 to facilitate the mounting of the usual aircleaner and silencer device (not shown).

Throttle valve 6 has an arm l2 rigidly secured to its shaft i3 and tothis arm there is connected a link I4 extending to the usual throttlepedal for manual control of the valve. Throttle ,I has a lever l5 rigidwith its shaft l6 and to the outer end of this lever is pinned a rod Hwhich is secured to the lower, movable end i8 of a bellows l 9. Thebellows is supported at its upper end by a bracket 20, secured to thebody of the carburetor, and an apertured lug 2i slidably receives andguides throttle operating rod ll. A tube 22 extends. to a port 23opening into mixture conduit i controlled by manual throttle 6 so thatthe suction conditions in this conduit are transmitted tobellows IS. Thebellows is preferably of the self-expanding or resilient type so as tonormally maintain suction controlled throttle I in its closed posit-ion,as shown, the

resilience of the bellows and the linkage being shown at 21. A main fuelpassage or nozzle 26 communicates with the fuel reservoir through acalibrated metering orifice 29 and discharges into the smallest orprimary venturi 3 in mixture conduit I. A second main nozzle 30communicates with the fuel reservoir through a calibrated meteringrestriction 3| and communicates with the smallest or primary venturi 4in second mixture conduit 2. Metering orifice or restriction 28 iscontrolled by a. -metering rod. 32 pinned at its upper end to a lever 33which is pivotally mounted at 34 and connected at its opposite end bymeans of a link 35 to an arm '36 rigid with manual throttle shaft 13.Metering pin 32 and its control linkage are arranged so that as manualthrottle 6 is opened, the metering pin will be raised so as toprogressively move smaller portions thereof into metering orifice i9 andthus enrich the mixture being discharged through mixture conduit I.

The second metering orifice 3| is controlled by a metering pin 40yieldingly connected at its upper endto a pivoted lever 4|, this leverbeing connected-at its end opposite pin 40 by means of a link 43 to anarm 44 rigid with suction controlled throttle shaft l6. Metering pin 40has an enlargement 45 positioned to seat against the upper edge oforifice 3| and cut off the communication between secondary and mainnozzle 30 and the constant level fuel reservoir wheneve throttle 1 issubstantially closed.

shot of fuel in the mixture conduit I when throttle 6 is opened. Anysuitable type of accelerating pump and valving may be provided.

In operation, the carbureting elements shown at the left side of thefigure, including mixture conduit I. main nozzle 26, idling system 48,Ill,

metering pin 32, and accelerating pump 64 function to. provide properlymetered fuel for all low speed operating conditions. The elements shownat the right side of the figure, including mixture conduit 2, idlingsystem 43, 5|, metering pin 40, and main nozzle provide a secondarycarburetor in which the idling system discharges substantiallycontinuously whenever port 49 is exposed to suction, but in which nofuel can be drawn from main nozzle 30 until the suction in mixtureconduit I is sumcient to indicate a predetermined speed, say miles anhour, at which the added fuel is desired, whereupon bellows I! will becontracted, opening throttle I and also valve enlargement controllingmetering orifice 3|.

There is thus formed in a compact, unitary carburetor, structure forinsuring the most eillcient discharge of fuel under low speed conditionswhile. at the same time, providing for greatly increased capacity underhigh speed conditions.

various features are conventional and these and When'throttle valves 6and l are substantially closed, fuel is supplied to mixture conduits land 2 through the usual idling ports 48 and 49 communicating with theconstant level reservoir through passages 50 and 5| having restrictions52 and 53 and air bleeds 54 and 55. Idling passage 50 supplying mixtureconduit I communicates with the enlarged lower portion 56 of main fuelpassage 28 posterior to metering restriction 29 so as to form aninterconnected idle in which all fuel for supplying both the main andidling passages flows through a single metering restriction.Idlingpassage 5| supplying the secondary mixture conduit 2, communicateswith the fuel reservoir by means of a port 58 which is indei pendent ofmain nozzle 30 so that fuel will be.

discharged from idling port 49 whenever throttle I is substantiallyclosed, regardless of the position of metering pin 40.

A third arm 60 is formed rigidly on manual throttle shaft l3 andconnected by a link 6| to .a lever pivotally-mounted at 63, the leverbeing connected at its other end to a piston rod 64 and piston 65forming an accelerating pump. Piston 65 operates in cylinder 66 so as todischarge a others may be modified in such respects as will occur tothose skilled in the art without departing from the spirit of theinvention. The exclusive use of all such modifications as come withinthe scope of the appended claim is contemplated.

We claim:

In a dual carburetor, a fuel reservoir, first and second inductionconduits having a common air inlet pipe and each having a venturi, mainfuel nozzles for supplying fuel from said reservoir to each of saidinduction conduits, throttle valves for each conduit, idling systems foreach of said conduits, the idling system for the first conduitcommunicating with the fuel nozzle-for said conduit and the idlingsystem for the second conduit communicating with, the fuel reservoirindependent of the second fuel nozzle, a metering pin controlling eachmain fuel nozzle, the metering pin for the fuel nozzle supplying thefirst induction tube being constructed and arranged to control the fuelflow to the idling system when the throttle valve for the firstinduction conduit is in closed position and the metering pin.controlling the main fuel nozzle to the second induction conduitincluding a valve constructed and arranged to close the fuel supply tosaid nozzle when the throttle valve for the second conduit is in closedposition, manual means for operating the throttle valve and metering pinregulating the fuel supply to the first conduit, and means controlled bythe pressure in the first conduit anterior to its throttle for operatingthe throttle valve and metering pin controlling the supply of fuel tothe second conduit.

GEORGE M. BICKNELL. ..VAN C. WORDEN.

